1. Field of the Invention
The present invention relates to waste tank servicing assemblies and more particularly to a combination of a fluid operated drain valve in combination with a reservoir and spray rinse apparatus adapted to be installed in an aircraft lavatory waste tank.
2. Description of the Prior Art
In most aircraft lavatory systems currently in use, a waste tank is provided in conjunction with the lavatory. During a flight, the waste tank, which may be used with a recirculating toilet system or, alternatively with a fresh water system, is utilized to retain human wastes. At the conclusion of the flight, the tank is drained by ground service personnel. During that process, the tank is rinsed out with a cleaning fluid which may include deodorants and disinfectants, and is provided with a predetermined quantity of precharge liquid (depending on the installation), prior to the next flight of the aircraft.
In waste systems of the prior art, the tank drain valve is connected through a cable assembly to a manual release mechanism, which is located at the service panel. As noted in U.S. Pat. No. 4,338,689, issued July 13, 1982 to Clifford V. Zieg and assigned to the assignee of the present invention, alignment problems were encountered with a valve that was manually operable through a cable. Prior art systems employed a long rigid extension tube to assure continued alignment of the valve in the valve seat. The patent to Zieg, however illustrated a novel, elastomeric valve plug which could accomodate some degree of misalignment and still form an adequate seal for the tank.
The tanks of the prior art also included a special fitting or nipple which was adapted to connect to a servicing vehicle. The vehicle supplied a cleaning and rinsing fluid which was applied to the interior of the tank through a spray system. After the drain valve was seated, the same spray system was used to impart a premeasured precharge to the tank.
In servicing a waste tank according to prior art, a technician would couple a waste line to the nipple at the service panel. The technician would then, manually, through the use of a cable system, open the drain valve, dumping the contents of the tank into the coupled waste line. A cleaning fluid line would then be connected to an appropriate intake port through which a combination of a cleaning and disinfecting fluid could be applied, through a spray line to clean the interior of the tank while the drain valve was kept open.
After a predetermined time interval, the drain valve would be closed by releasing the cable. The tank was then precharged by permitting additional, rinsing/cleaning fluid to be supplied for a timed interval or until the predetermined quantity of fluid had been furnished.
The prior art system became a source of at least two major problems, even with the modified drain plug of the Zieg invention. One problem was cable side loads which made actuation difficult and which contributed to breakage. A partial disassembly of the tank and aircraft was required to reinstall a new cable system. In addition, the elements of the cable system required service and maintenance and, because of the hostile environment, from time to time would become inoperable, preventing the operation of the drain valve.
A second, potentially more serious problem is caused by the service technician, when, either through inattention or carelessness, fails to shut off the cleaning/rinsing supply after the specified time interval has elapsed. As a result, the tanks are given an excessive precharge. In some instances, this would only require a premature limit on the usage of the lavatory, since, once the tank is determined to be full, further usage is prohibited. Since this circumstance will occur during the flight, the lavatory must be taken out of service. In those aircraft which have a common tank for all of the lavatories, such an excessive precharge might require a shut down of all lavatories part way through a busy flight on a crowded aircraft, to the great distress and inconvenience of passengers and crew.
A more serious consequence of an overflow of the tank during servicing is the possibility of serious structural damage to the aircraft. The cleaning/rinsing fluid tends to be highly corrosive to metallic parts and any overflow into the lavatory compartment or into the inaccessible interior of the fuselage of the aircraft, creates a potential hazard to the integrity of the structural and control elements of the aircraft.
What is needed, and what has been provided in the present invention, is a system that automatically opens the drain valve upon the application of the cleaning/rinse fluid and, at the same time provides a predetermined quantity of precharge fluid to the tank, specific to the type of aircraft being serviced without any special attention required of the service technician.